1. Field of the Invention
The invention relates to a semiconductor memory, particularly to a semiconductor memory capable of writing and reading data in units of a predetermined plurality of memory cells.
2. Description of the Related Art
Semiconductor memories include random access memory in which data can be freely read and written, and read only memory which is dedicated for reading previously written data. The read only memory is generally composed of a nonvolatile semiconductor memory. As for the read only memory, there is a memory capable of electrically rewriting data (erasing written data and writing another data). The semiconductor memory includes a memory capable of erasing data in a batch.
As for a memory capable of electrically rewriting data, there is a memory capable of writing and reading data in unit of predetermined plural memory cells (predetermined plural memory cells are defined as banks) relative to a memory cell array composed of plural memory cells incorporated in the memory.
High speed access (reading and writing) has been recently required in a semiconductor memory. To realize a high speed access, a semiconductor memory capable of reading and writing in unit of bank requires access to every bank independently. Particularly, it is required to independently and efficiently access respective banks after confirming access status of respective banks. However, a semiconductor memory satisfying these requirement has not been developed hitherto.
A semiconductor memory has a tendency to include more pins as terminals through which signals are supplied. In a semiconductor memory capable of reading and writing data in unit of bank, it is preferable to avoid the provision of output terminals for signals to instruct access status in order to confirm the access status of respective banks. The reason is that if the number of terminals are increased, a scale of the semiconductor memory is increased, leading to the increase of cost.
It is therefore an object of the invention to provide a semiconductor memory capable of realizing the access to respective banks efficiently and independently upon confirmation of access status of respective banks.
It is another object of the invention to provide a semiconductor memory capable of realizing the access to respective banks efficiently independently without increasing the number of terminal for confirming access status of respective banks.